Why Shouldn't You Reuse Frying Oil? Learn How to Recycle It Here

Reusing frying oil can compromise your health in the long run. Instead of reusing it, learn how to recycle it to take care of your health and the planet.
Why Shouldn't You Reuse Frying Oil? Learn How to Recycle It Here

Written by Editorial Team

Last update: 11 June, 2023

The use of frying oil is practiced in millions of kitchens around the world, and the question arises as to whether it’s possible to reuse it safely. Some people think that reusing oil is a viable practice, as long as certain guidelines are followed, such as filtering it and storing it properly.

On the other hand, there are concerns about the quality of used oil, such as the accumulation of harmful compounds and the degradation of nutrients. In this article, you will learn whether or not it’s possible to safely reuse frying oil and some ways you can recycle it.

Reusing frying oil

Reusing frying oil has been the subject of debate, and there are different opinions about its feasibility. Before considering reusing oil, it’s important to consider several factors.

These include the initial quality of the oil, the type of food that has been cooked in it, and the method of storage used.

In fact, a report published by the Organization of Consumers and Users (OCU) in Spain explains some guidelines that should be followed in order to be able to reuse oil up to 25 times. Among them are: do not let the oil cool, do not let the temperature exceed 180°C, use a deep fryer and fry continuously.

However, it’s important to note that these guidelines are difficult for most consumers to follow at home. The reality is that people do not have specialized equipment or the capacity to precisely control the cooking temperature or to carry out a continuous frying process.

In addition, it’s important to keep in mind that each time oil is reused, the risk of degradation and accumulation of harmful compounds increases. Even if the above recommendations are followed, the quality and safety of the oil may decrease with time and repeated use.

Is it safe for health to reuse oil?

The question of whether it’s safe to reuse frying oil is crucial when considering its use in cooking. While there are different perspectives on this issue, it’s important to consider the reasons behind the position that it’s unhealthy to reuse oil. Here are some of these reasons.

Accumulation of harmful compounds

With each use, oil is exposed to high temperatures and chemical degradation occurs. This degradation can result in the formation of toxic and harmful compounds, such as acrylamide, which, according to the U. S. National Cancer Institute, increases the risk of several types of cancer.

Also, as the oil is repeatedly heated, free radicals are produced. These free radicals are capable of degrading the cells of our body, thus deteriorating our health and making us more prone to suffer from diseases.

All this occurs when frying at temperatures above 100 °C, which is easy to reach and go beyond when frying something in our homes.

We think you may also enjoy reading this article: What Is Filé Powder and How Is It Used in Cooking?

Increased trans fat content

The heating and reuse of edible fats and oils lead to chemical changes, such as the formation of trans fatty acids(TFA), which are linked to cardiovascular disease.

In fact, a study published in the journal Food Chemistry investigated the effect of heating/frying on TFA formation in six common types of fats/oils in India. TFA was measured before and after heating/frying at different temperatures. All oils/fats showed an increase in TFA, saturated fatty acids, and a decrease in unsaturated fatty acids.

Increased absorption of toxic compounds

When reused oil is used in food frying, it permeates further into the new food, resulting in an increase in its fat content. At the same time, toxic compounds are introduced into the final product that we are going to ingest, increasing the possibility of their penetration into our organism.

With each reuse cycle, both the number of toxic compounds and their capacity to penetrate the food increase, generating greater contamination in our food.

These are some of the reasons why you should not reuse oil for frying, especially if you are frying different types of food that need different temperatures to achieve cooking.

To this we can add the risk of suffering an allergic reaction or food poisoning when exposed to foods that have been through the same oil that has already been used for frying allergenic or sensitive foods.

When frying different types of food with different temperature requirements, it’s advisable to opt for fresh oil on each occasion to ensure proper cooking and avoid the accumulation of harmful compounds.

How to recycle used oil

Instead of pouring used oil down the drain or throwing it in the trash, recycling offers several ways to take advantage of this resource and reduce its negative impact on the environment. Used oil, if managed correctly, can be recycled and transformed into useful products. Learn about some ways to recycle it below.

Make soap

Making soap from used oil involves mixing clean, filtered oil with caustic soda in an appropriate ratio. This process, called saponification, turns the oil into soap by binding the fatty acid molecules with the caustic soda molecules.

Once saponification is complete, additional ingredients, such as essential oils, can be added and the mixture is poured into molds to cure for several weeks. At the end of the process, natural and environmentally friendly homemade soap is obtained.

Create decorative candles

Making candles from used oil is a simple and creative process. To begin, a spiral base is created with wire, leaving an ascending section to hold the cotton thread. This base is placed in the center of the selected container.

Next, the container is filled with the previously filtered used oil, making sure to cover the cotton wick. If desired, a few drops of aromatic oil can be added to give fragrance to the candles. Once completed, the result is a recycled candle ready to be lit and enjoyed.

This process offers an eco-friendly way to take advantage of used oil, reducing waste and providing personalized and environmentally friendly candles.

Like this article? You may also like to read: Lobster: Nutritional Value, Benefits and Uses in Cooking

Grease the molds of your desserts

The molds used to make cakes, cookies, and other preparations in the oven, can be greased with oil previously filtered to facilitate the food to come out faster and without problem. To do this, you will only need to filter the oil and spread it lightly with a kitchen brush on the mold and then pour the mixture of the preparation.

Create an oil lamp

You can create an oil lamp using a heat-resistant container, a wick, and the oil used as fuel. Fill the container with the oil and dip the wick into it. Light the wick and you will have a homemade lamp that will be useful in emergency situations or for decorative lighting.

We need to improve our consumption habits

In a world where sustainability and environmental preservation are increasingly important, it’s essential to reflect on our consumption habits, including the way we treat used oil. Reusing and recycling frying oil are practices that invite us to reconsider the way we handle this resource and the impacts we generate on our environment.

As we explore the possibility of reusing frying oil, we find that there are factors to consider and limitations that make us question whether it’s safe or suitable for our health and the environment. While some experts and studies offer guidelines and recommendations for reuse, it’s important to be aware of the limitations and associated risks.

On the other hand, recycling used oil offers creative and environmentally friendly alternatives, such as soap and candle making. These forms of recycling not only allow us to give oil a second life, but also encourage waste reduction and the use of more natural and sustainable products.


All cited sources were thoroughly reviewed by our team to ensure their quality, reliability, currency, and validity. The bibliography of this article was considered reliable and of academic or scientific accuracy.



This text is provided for informational purposes only and does not replace consultation with a professional. If in doubt, consult your specialist.